Electrostatic spray coating apparatus

ABSTRACT

Electrostatic spray coating apparatus including means for mechanically atomizing coating materials and means for electrostatically charging and depositing the atomized material onto articles, characterized by the features, individually and collectively, of an improved material-charging electrode, improved means for sealing the material passages from the remainder of the apparatus and for contributing to efficient and effective charging of the material, improved conductor means for carrying a charge of high potential to the material-charging means and including means insuring safety of the apparatus, and enhanced overall construction of the apparatus for greater service life, more reliable and safe operation, and economy.

United States Patent [72] Inventors Patrick D. Shaffer Westmont, lll.; Duane D. Krohn, Arvada, Colo. [2l] Appl. No. 827,268 [22] Filed May 23, 1969 [45] Patented June 8, 1971 [73] Assignee Binks Manufacturing Company Chicago, Ill.

[54] ELECTROSTATIC SPRAY COATING APPARATUS 11 Claims, 6 Drawing Figs.

[52] U.S.Cl 239/15, I 239/583 [5 1] Int. Cl B05b 5/00 [50] Field ofSearch 239/l5,3, 583, 412

[56] References Cited UNITED STATES PATENTS 3,339,841 9/1967 Beach, Jr 239/15 3,382,091 5/1968 Drum i.

ABSTRACT: Electrostatic spray coating apparatus including means for mechanically atomizing coating materials and means for electrostatically charging and depositing the atomized material onto articles, characterized by the features, individually and collectively, of an improved material-charging electrode, improved means for sealing the material passages from the remainder of the apparatus and for contributing to efficient and effective charging of the material, improved conductor means for carrying a charge of high potential to the material-charging means and including means insuring safety of the apparatus, and enhanced overall construction of the apparatus for greater service life, more reliable and safe operation, and economy.

PATENTED JUN 8 I911 sum 2 BF 3 ELECTROSTATIC SPRAY COATING APPARATUS BACKGROUND OF THE INVENTION Manual and automatic spray guns for mechanical atomization and electrostatic deposition of coating materials such as paint, lacquer, varnish and the like are known from such previously issued U.S. Pat. Nos. as 2,805,642; 3,048,498; 3,l69,882; 3,169,883; 3,25l,55l; 3,253,782; 3,268,17l; etc. In general, the material is atomized from a nozzle by impinging streams of air on a stream of the material (air atomization) or by forcing the material through an appropriately shaped nozzle under adequate hydraulic pressure (hydraulic atomization). Atomization may also be effected by centrifugal force and by electrostatic forces. As the material is atomized, an electrostatic charge is imparted to the coating material which causes the charged particles of atomized material to be attracted to workpieces or articles which are purposely grounded, whereby to cause most of the material to be deposited on the work.

SUMMARY OF THE INVENTION A primary object of this invention is to provide improved means for electrostatically charging the coating material, especially to insure effective charging of each particle in the atomized spray to enhance its attraction to the grounded work.

Another object is to provide optimum safety in use and operation of electrostatic spray guns.

A further object is to provide an improved spray gun of great reliability and serviceability Yet another object is to facilitate electrostatic spray coating with both nonconductive coating materials and conductive coating materials.

Other objects and advantages will become apparent from the drawings and the following description, which are given for the purpose of acquainting those skilled in the art with the manner of making and using our invention, and especially with the best mode presently contemplated by us of carrying out our invention.

THE DRAWINGS:

FIG. I is a perspective view of a manually operated, air atomizing, hand spray gun embodying our invention;

FIG. 2 is an exploded perspective view of the forward or barrel portion of the gun;

FIG. 3 is a vertical longitudinal section of the gun taken on an enlarged scale;

FIG. 4 is a vertical section of the nozzle portion of the gun taken on a further enlarged scale;

FIG. 5 is a longitudinal section of the charging conductor for the gun; and

FIG. 6 is a vertical longitudinal section of an automatic air atomizing spray gun embodying our invention.

DESCRIPTION The hand gun of FIGS. 1 through 5 is comprised ofa conductive handle portion 10, an insulating barrel portion 11, and an insulating nozzle assembly 12.

The handle 10 is in essence the handle conventional for airatomizing paint spray guns, the same being formed of metal and including an air inlet 13, an air valve 14, a material control valve 15, a pivotally mounted trigger 16 for operating the valves 14 and 15, and an assembly 17 for controlling fan air.

The barrel 11 is formed of insulating material and includes a main body 20 and a pair of tubes inclined downwardly and rearwardly from the body, namely a paint or coating material supply tube 21 and a tube 22 for reception of a charging conductor. By virtue of the downward and rearward inclination of the tubes 21 and 22, the inlets for the material and air hoses and the inlet for the charging conductor are disposed adjacent one another to accommodate a neat and easily handled assembly of flexible conduits leading to the gun that can be easily controlled and manipulated by the gun operator.

As shown in FIG. 3, the barrel body 20 has a longitudinal air passage 23 communicating with the air passage in the handle to which air is supplied under control of the valve 14. At the forward end of the body, a pair of air ports communicate with this passage, namely, a port 24 for supply of atomizing air and a port 25 for supply of fan air. The latter port is under the control of the assembly 17 which comprises a headed conductive screw thread into and adjustable in the handle 10 and including a threaded stem 18 to which is detachably secured a valve stem 26 formed ofinsulating material, the stem 26 terminating in a valve head 27 adjustable relative to the rearward end of port 25 whereby to control the amount of air passing to and through said port.

The barrel body 20 also includes an axially extending passage 28 aligned with and receiving the material control valve 15. The valve 15, which is in the form of an elongate rod, stem or needle, extends forwardly from the handle 10 through the trigger 16 and a packing assembly or gland including a nut or screw 29 threaded into the rearward end of the passage 28. Immediately within the passage 28, the metal stem is terminated and an insulating stem 30 is threaded thereto, the stem 30 extending forwardly to adjacent the front of the barrel in proximity to the paint or material inlet and terminating in a reduced and threaded extension.

The nozzle assembly 12, which is formed entirely ofinsulating material, is of essentially conventional design and comprises a material nozzle 31 and an air nozzle 32 both threadedly attached to the front of the barrel body 20 in axial alignment with the needle valve passage 28, in the manner conventional in the art.

The material nozzle 31 is threaded into a counterbore in the forward end of the body 20 and includes an axial bore 33 aligned with the passage 28 and comprising a port for paint or coating material. At its forward end, the bore is necked down to form a conical valve seat 34 (on which the material valve seats) and a small diameter outlet for discharge of a solid stream or jet of coating material. Radially outward of the bore 33, the material nozzle includes second longitudinally extend ing port means (not shown) which communicate with the air port 24 in the body 20 and conduct air into a chamber 35 defined between the material nozzle and the air nozzle. At its center, the air nozzle is formed to define port means, here shown as an annular opening 36 surrounding the material outlet, for impinging air onto the discharging stream of coating material to atomize the material into small discrete particles.

The atomized spray of paint or other coating material, ab sent further control thereover, would issue from the nozzle in the form of a gradually expanding conically shaped spray and would be deposited on the work in a circular pattern. If such pattern is desired, the control means 17 is adjusted to seat the valve head 27 in the port 25. Usually, however, it is desired to convert the conical spray into a fan-shaped spray so as to deposit coating material on the work in a rectangular or elliptical pattern. For this purpose, the air nozzle 32 includes a pair of opposed ears 37 provided with ports 38 for impinging streams of air onto opposite sides of the atomized spray whereby to force the spray into a flat or fan-shaped pattern. Air is supplied to the ports 38 in the cars 37 through holes in the air nozzle and radially outer air ports 39 in the material nozzle 31 which communicate with the port 25 in the barrel body. The amount of air admitted to the ports 38, and thus the degree of fanning or shaping of the spray pattern, is controlled by the assembly 17 and the valve head 27.

According to the present invention, the coating material is supplied to the gun body immediately to the rear of the material nozzle 31. For this purpose, in the embodiment of FIGS. 1 to 5, the body includes a passage 40 extending from the passage 28 to the material inlet tube 21. At approximately the point where the passage 40 enters the passage 28, a conductive extension 41 is threaded to the forward end of the insulated part 30 of the material valve, and to this is threadedly attached a conductive valve and charging needle member 42.

The member 42 comprises a conical portion mated to conical seat 34 of the material nozzle and adapted to seat thereon to close the material outlet of the gun, the valve normally being engaged with its seat under the bias of a valve spring mounted in the handle of the gun. Projecting forwardly from the valve portion of the member 42 is a small diameter, preferably pointed, charging needle 43 which projects from the seat through and forwardly of the material outlet into the area where the material is atomized into a spray. The member 42 is detachably mounted on the valve stem 30-41 to facilitate ready replacement of the member 42 for two purposes, namely (1') to replace the member when the charging needle 43 becomes badly bent or is broken off due to mishandling of the gun and (2) to accommodate selective exchange of members having different valving characteristics.

To seal the rearward end of the portion of the passage 28 that receives paint or coating material, an expandable and contractable bellows 44 encircles the needle valve at and to the rear of the point of entry of the paint supply passage 40. The bellows includes an integral fitting 45 at its forward end which is sealingly clamped between the stem parts 30 and 41, and an integral fitting 46 at its rearward end which is sealingly secured against a radial shoulder in the barrel body by means of a tube 46a of insulating material that extends between said shoulder and the packing gland screw 29', the stem 30 extending slidably through the tube 46a and the fitting 46. The bellows is expandable to accommodate forward movement of the material valve to engage the valve member 42 with its seat 34 under the bias of the valve spring in the handle; and is contractable to accommodate rearward movement of the needle valve upon actuation of the trigger 16 to open the outlet and accommodate discharge of coating material. The bellows provides an excellent seal of long and effective service life.

In the embodiment of FIGS. 1 to 5, the bellows is formed of conductive metal and constitutes part of the electrostatic charging equipment of the gun. In particular, a conductor 47 engaged with the fitting 46 is potted within a rearwardly and downwardly inclined passage in the barrel body which extends to the tube 22, the conductor 47 terminating at the upper end of said tube in a short rigid pin or terminal.

The tubes 21 and 22 are physically united to the barrel body 20 by a process we call spin-welding." Specifically, the tube and the body are formed of thermosetting materials and each tube and the respective bore in the body have mating conical end portions. Each tube is inserted in its bore and then rotated therein at sufficient speed and under sufficient compressive force to develop friction heating of the mating surfaces of the material to a temperature at or slightly in excess of their melting temperatures, whereupon the rotation is stopped and the mating surfaces become integrally fused. In this manner, a structurally solid and leak-proof bond is attained between the body and the tube 21, and a structurally solid bond ofinsulating integrity is attained between the body and the tube 22.

The tube 22 is adapted for close tolerance and formfitting reception therein of a rigid probe 48 mounted on the end ofa high-voltage conductor 49 for carrying a high-voltage charge to the gun. The conductor, which is flexible, comprises a coaxial cable including a central conductor 50 having an insulating sheath 51, a conductive grounding sleeve or braid 52 encircling the sheath 5], and an encasing sheath 53 of insulation. At the probe 48, the conductor 50 and sheath 51 extend through a metal or conductive fitting 54, the sleeve 52 is conductively connected to an extension on the fitting, and the cable is secured to the fitting by a clamp 55.

Forwardly of the fitting 54, one end portion ofa rigid sleeve 56 of insulating material is spun-welded, in the same manner as above described, to the insulating sheath 51 of the conductor S0. The sheath 51 terminates within the sleeve 56, and the terminal portion of the conductor 50 projects forwardly of the sheath into said sleeve. The forward end of said sleeve is adapted for reception of a resistor assembly comprising a resistor element 58 and a pair of conductive end caps 59. The end caps 59 are each a rounded element having a conical receptor depression therein for receiving and guiding a conductor into contact with the resistor element 58, i.e., the conductors 50 and 47. The resistor assembly is slipped into the sleeve 56 and is encased therein by a suitable insulating compound 57 completely eliminating the possibility of voids or airgaps, It is this assembly of the fitting 54, the sleeve 56 and the resistor assembly that constitutes the rigid probe 48.

The particular virtue of the probe assembly is that a workman cannot possibly become exposed to or have engagement with the high tension cable 50 directly. If the resistor is in place, the individual is separated from the high-tension cable by the safety factor of the limiting resistor. If the resistor is not in place, the terminal of the high-tension cable 50 is still deeply embedded in the protective sleeve 56 so that the operator cannot come in contact with it. Thus, there is complete safety.

To render this safety feature of the hand gun fully effective, we prefer to solidly pot the resistor in the sleeve 56 by a permanently set insulating adhesive, whereby the safety resistor is always in place to protect the operator when the gun is disassembled for cleaning and maintenance. In addition, and of primary import, the resistor performs a particular safety function in operation of the gun as is explained in greater detail in US. Pat. No. 3,048,498.

As above indicated, the probe 48 is slidably insertable into and removable from tube 22 in formfitting relation therewith. As the probe is inserted into the tube, the fitting 59 on the outer end thereof guides the terminal portion of the conductor wire 47 into engagement with the resistor 58, whereby to establish a conductive path from the conductor 50 through the resistor 58 to the conductor 47, the bellows 44, the stem part 41, the valve member 42 and the charging needle 43. In this conductive path, there are no airgaps, exposed sharp corners or other impediments that might give rise to a dielectric breakdown, corona discharge or the like. Nevertheless, to insure complete safety, the tube is encased, over the critical portion thereof, with a grounding shield 60 for protection of the operator.

As will be appreciated, the electrostating coating materialcharging components of this gun consist of the bellows 44, the stem member 41, the valve member 42 and the charging needle 43. These members are directly coupled to the high-tension conductor 50 and are otherwise widely insulated from the remaining metal components of the gun. Paint entering and passing through the gun via the tube 21 and the passages 40, 28 and 33 contacts the bellows 44 and the members 41 and 42 and is atomized in the presence of the charging needle 43, whereby essentially all of the discrete particles of the spray are efficiently and effectively charged to high electrostatic potential for efficient deposition on a grounded article of work.

At the same time, the operator is afforded optimum safety by virtue of electrical grounding of all components with which he may come in contact. Specifically, the gun handle 10, the grounding shield 60, and the material supply hose are commonly grounded via the grounding sheath 52 of the cable 49 by means of a conductive strap 61 interconnecting conductive inlet fittings on the air inlet 13, the material inlet 21 and the electrical receptor 22, the latter of which receives and becomes electrically connected to the conductor fitting 54 on the power supply cable. In this manner also, the gun operator is grounded through the gun handle whereby he does not and cannot become a capacitive influence in the electrostatic system.

A further advantage of the gun of this invention is its ability to handle conductive as well as nonconductive coating materials. By utilizing an insulating fitting 62 on the material inlet tube 21, appropriately increasing the insulating value of the material inlet, as by use of an interior insulating sleeve, and selecting an appropriately insulating material supply hose, conductive paint would become so widely and effectively insulated from the grounded components of the system as to facilitate atomization and electrostatic charging of conductive paints.

In this manner, we have provided an extremely useful and highly efficient electrostatic hand spray gun of great safety, long service life, lightweight, convenient handling, and aesthetically pleasing design.

The same and/or comparable features can also be embodied in automatic spray guns. For example, we have shown in FlG. 6 one embodiment of an automatic spray gun provided in accordance with this invention. This gun comprises a conductive mounting and operating section 110, an insulating barrel 111 and an insulating nozzle assembly 112. The nozzle assembly 112 and the air supply therefor are essentially the same as previously described (except that the air supply conduit is offset from the plane on which FIG. 6 is taken and therefore not visible in that view) and thus need not be redescribed here.

The operator section 110 includes an air valve 114, a material control needle valve 115 and a pneumatically operated piston 116 for operating both said valves. The body of this section is provided with appropriate inlets in its rear face (not shown) for individual supply of air to the valve 114 and the piston 116, and is also provided with a hole 119 for reception of a mounting rod.

The barrel 111 is formed of insulating material and comprises a blocklike body 120 having an axial bore 128 therethrough aligned with the nozzle assembly 112 and adapted for passage of the stem members of the material valve 115. A metallic stern member extends forwardly from the operator section 110 and has threaded connection within the body 120 with an insulating stem member 130 which extends forwardly to adjacent the front of the barrel.

Coating material is supplied to the gun immediately to the rear of the nozzle assembly by means ofa radial inlet port provided with an appropriate insulated inlet fitting 140 which may be straight or ofelbow style.

At the point where the fitting 140 enters the barrel body, a conductive extension 141 is threaded to the forward end of the insulated valve stem 130 and a conductive valve and charging needle member 142 is detachably secured to the extension 141. The member 142 has a conical nose portion adapted to seat upon the valve seat of the material nozzle to close the material outlet, and a charging needle 143 extending axially through the material outlet to the area of paint atomization. As previously described, the member 142 is detachably mounted to facilitate replacement thereof.

To the rear of the material inlet, the coating material passage is sealed closed by a bellows 144 having a front fitting 145 sealingly clamped between the needle parts 130-141 and a rear fitting 146 sealingly clamped between a shoulder in the passage 128 and a valve stem-encircling tube 146a fixed in place by a tubular screw 129 threaded into the rearward end of the bore 128.

In the embodiment of FIG. 6, a electrical connection to the valve member 142 and charging needle 143 is achieved by a washer 147 engaging the extension 141. In this case, the bellows 144 may be either conductive to attain the paint charging characteristics previously described, or may be formed of insulating materials so as to reduce capacitance. ln the present state of the art, metal bellows have considerably greater service life than plastic bellows, and therefore metal is currently preferred. However, when plastic bellows are developed to a higher state of perfection, the gun designer will be afforded a further selection of balance between capacitance and charging capability.

As shown in FIG. 6, the conductive washer 147 is engaged with a stud 1470 which in turn is engaged by a button 147!) that is held in position by a spring 1470 confined between the button and a safety resistor 158. The resistor, the spring and the button are mounted within a conductor receptor passage 122 in the gun body and are adapted to be connected to an appropriate power supply by a power supply cable (not shown) similar to the cable 49 and its fitting 54. In this case, however, the cable itself does not embody the safety resistor and thus does not have all the safety features of the embodiment of FIGS. 1 to 5. However, automatic guns are usually attended by skilled technicians and therefore do not require the same degree of built-in safety in cleaning and maintenance as do hand guns. Thus, while the probe structure of FIG. 5 is preferred, it may be feasible, especially in automatic guns, to embody the resistor in the gun.

As before, the metallic components of the operator section of the gun are grounded through the shield of the conductor cable to insure safe operation of the gun.

As constituted pursuant to the disclosure of FIG. 6, we have provided an automatic electrostatic spray gun that is highly efficient, safe in operation, of long service lifc, and compact and convenient design.

Also, because the coating material inlet is widely insulated from the grounded components of the gun, the automatic gun, like the hand gun, is adapted to atomize and electrostatically charge conductive as well as nonconductive coating materials.

Thus, the objects and advantages of the invention have been shown to be achieved in a convenient, economical and practical manner.

While we have shown and described what we regard to be the preferred embodiments of our invention, it is to be appreciated that various changes, rearrangements and modifications may be made therein without departing from the scope ofthe invention, as defined by the appended claims.

We claim:

1. ln electrostatic spray apparatus having an electrically insulating body including a material passage terminating in an outlet orifice, a valve for opening and closing said orifice including an electrically insulating stem extending through said passage, the improvement comprising electrically conductive means sealing the stem to the body, electrically conductive means on said stem connected to the first-named conductive means extending to and through the orifice, and a power lead connected to one of said conductive means for causing both said conductive means to charge material passing through said passage and said orifice, said conductive means being the sole electrically charged means contacted by the material.

2. In the apparatus of claim 1, said first-named conductive means comprising a metal bellows fixed at one end to the body and at its other end to the conductive part of the stem.

3. In the apparatus ofclaim 1, the second named conductive means comprising a charging needle detachably secured to the stem and extending through the orifice.

4. 1n the apparatus of claim 1, the second-named conductive means comprising a combined charging needle and valve member detachably secured to the stem and adapted to be replaced to accommodate variation in valve characteristics and in the event of damage to the charging needle.

5. ln the apparatus of claim 1, said power lead comprising a conductor terminating in an integral insulated probe, a resistor embedded in the insulated probe and connected at one end to the conductor, and quick detachable connection means embedded in the other end of the probe for connection with the first-named conductive means.

6. ln electrostatic spray apparatus having an electrically insulating body including a material passage terminating in an outlet orifice, and a valve for opening and closing said orifice including an electrically insulating stem extending through said passage, the improvement comprising an electrically insulating material inlet communicating with said passage substantially immediately to the rear of said outlet orifice, an electrically conductive bellows in said passage substantially immediately to the rear of said inlet fixed at one end to the body and at its other end to the stem for sealingly closing said passage, electrically conductive stem means secured to said stem and said bellows at said other end of said bellows and extending to and through said orifice, and means for carrying a high electrostatic charge to said bellows and said conductive stem means to charge material passing from said inlet through said outlet.

7. ln electrostatic spray apparatus having an electrically insulating body including a material passage terminating in an outlet orifice, a valve for opening and closing said orifice ineluding an electrically insulating stem through said passage, and an electrically conductive normally grounded stem operating section mounted on said body at the end thereof remote from said orifice, the improvement comprising electrically insulating material inlet means spaced from said grounded section and communicating with said passage substantially immediately to the rear of said outlet orifice, means in said passage substantially immediately to the rear of said inlet for sealingly closing said passage, electrically conductive stem means secured to said stem forwardly of said sealing means and including a charging needle extending to and through said orifice, and means for carrying a high electrostatic charge to said conductive stem means to charge material passing from said inlet means through said outlet, said body and stem being elongate and said body, stem and inlet means being formed of high dielectric material for electrically isolating coating material from said grounded section whereby to accommodate spraying of both nonconductive and conductive coating materials.

8. ln electrostatic spray apparatus having an electrically insulating body including a material passage terminating in an electrically insulating outlet orifice, and a valve for opening and closing said orifice including an electrically insulating stem extending through said passage, the improvement comprising a material inlet communicating with said passage substantially immediately to the rear of said outlet orifice, means in said passage substantially immediately to the rear of said inlet for sealingly closing said passage, electrically conductive stem means detachably secured to said stem forwardly of said sealing means and extending to and through said orifice, and means for carrying a high electrostatic charge to said conductive stem means to charge material passing from said inlet through said outlet, said sealing means comprising an electrically conductive bellows having an electrically conductive fitting at one end detachably but sealingly clamped between said stem and said conductive stem means, said passage including a shoulder, said bellows having a fitting at its other end engaging said shoulder, and means detachably secured in said passage sealingly clamping the second-named fitting to said shoulder, said bellows aiding in the electrical charging of the coating material and being readily replaceable in the event of damage thereto, said conductive stern means comprising a member including a valve for opening and closing said outlet orifice and a charging needle extending through said orifice, said member being detachably mounted on said stem for ready replacement in the event of damage to the charging needle and/or to accommodate variation in valve characteristics.

9. ln electrostatic spray apparatus having a conductor for carrying a high electrostatic charge to the apparatus, an electrically insulating sheath thereabout, an electrically insulated tubular probe fixedly secured at one end thereof to said sheath, said sheath terminating within said probe and said conductor having a terminal portion projecting into said probe beyond said sheath but deeply seated within said probe, and a resistor inserted in the other end of said probe engaging the terminal of said conductor at one end thereof; the improvement comprising a terminal at the other end of said resistor located adjacent the end of but seated entirely within the probe and having therein quick detachable connection means for connection with the apparatus, and an insulating compound potting said resistor within said probe without airgaps.

l0. Electrostatic spray apparatus comprising an electrically conductive normally grounded handle including a valveoperating trigger, an electrically insulating barrel and valve stem projecting forwardly from the upper end of the handle and the trigger, an electrically insulating nozzle assembly on the forward end of the barrel, a material inlet at the forward end of said barrel rearwardly of the nozzle assembly, an electrically insulating material supply tube inclined downwardly and rearwardly from the material inlet toward the lower end of the handle, conductive elements in the material-receiving portion of the barrel between said inlet and said nozzle assembly,

means for carrying a high electrostatic c har e to said conductive elements inc uding an electncally insu ating conductorreceiving tube generally paralleling said material supply tube, and a strap joining the lower ends of the handle and said tubes for physically supporting said tubes, said barrel, stem and material supply tube electrically isolating coating material from said grounded handle to accommodate spraying of both conductive and nonconductive coating materials.

11. The apparatus of claim 10, including a ground fitting on the lower end of said conductor-receiving tube and a ground sheath of said tube connected to said fitting, said strap being electrically conductive and conductively secured to said fitting and handle. 

2. In the apparatus of claim 1, said first-named conductive means comprising a metal bellows fixed at one end to the body and at its other end to the conductive part of the stem.
 3. In the apparatus of claim 1, the second named conductive means comprising a charging needle detachably secured to the stem and extending through the orifice.
 4. In the apparatus of claim 1, the second-named conductive means comprising a combined charging needle and valve member detachably secured to the stem and adapted to be replaced to accommodate variation in valve characteristics and in the event of damage to the charging needle.
 5. In the apparatus of claim 1, said power lead comprising a conductor terminating in an integral insulated probe, a resistor embedded in the insulated probe and connected at one end to the conductor, and quick detachable connection means embedded in the other end of the probe for connection with the first-named conductive means.
 6. In electrostatic spray apparatus having an electrically insulating body including a material passage terminating in an outlet orifice, and a valve for opening and closing said orifice including an electrically insulating stem extending through said passage, the improvement comprising an electrically insulating material inlet communicating with said passage substantially immediately to the rear of said outlet orifice, an electrically conductive bellows in said passage substantially immediately to the rear of said inlet fixed at one end to the body and at its other end to the stem for sealingly closing said passage, electrically conductive stem means secured to said stem and said bellows at said other end of said bellows and extending to and through said orifice, and means for carrying a high electrostatic charge to said bellows and said conductive stem means to charge material passing from said inlet through said outlet.
 7. In electrostatic spray apparatus having an electrically insulating body including a material passage terminating in an outlet orifice, a valve for opening and closing said orifice including an electrically insulating stem through said passage, and an electrically conductive normally grounded stem operating section mounted on said body at the end thereof remote from said orifice, the improvement comprising electrically insulating material inlet means spaced from said grounded section and communicating with said passage substantially immediately to the rear of said outlet orifice, means in said passage substantially immediately to the rear of said inlet for sealingly closing said passage, electrically conductive stem means secured to said stem forwardly of said sealing means and including a charging needle extending to and through said orifice, and means for carrying a high electrostatic charge to said conductive stem means to charge material passing from said inlet means through said outlet, said body and stem being elongate and said body, stem and inlet means being formed of high dielectric material for electrically isolating coating material from said grounded section whereby to accommodate spraying of both nonconductive and conductive coating materials.
 8. In electrostatic spray apparatus having an electrically insulating body including a material passage terminating in an electrically insulating outlet orifice, and a valve for opening and closing said orifice including an electrically insulating stem extending through said passage, the improvement comprising a material inlet communicating with said passage substantially immediately to the rear of said outlet orifice, means in said passage substantially immediately to the rear of said inlet for sealingly closing said passage, electrically conductive stem means detachably secured to said stem forwardly of said sealing means and extending to and through said orifice, and means for carrying a high electrostatic charge to said conductive stem means to charge material passing from said inlet through said outlet, said sealing means comprising an electrically conductive bellows having an electrically conductive fitting at one end detachably but sealingly clamped between said stem and said conductive stem means, said passage including a shoulder, said bellows having a fitting at its other end engaging said shoulder, and means detachably secured in said passage sealingly clamping the second-named fitting to said shoulder, said bellows aiding in the electrical charging of the coating material and being readily replaceable in the event of damage thereto, said conductive stem means comprising a member including a valve for opening and closing said outlet orifice and a charging needle extending through said orifice, said member being detachably mounted on said stem for ready replacement in the event of damage to the charging needle and/or to accommodate variation in valve characteristics.
 9. In electrostatic spray apparatus having a conductor for carrying a high electrostatic charge to the apparatus, an electrically insulating sheath thereabout, an electrically insulated tubular probe fixedly secured at one end thereof to said sheath, said sheath terminating within said probe and said conductor having a terminal portion projecting into said probe beyond said sheath but deeply seated within said probe, and a resistor inserted in the other end of said probe engaging the terminal of said conductor at one end thereof; the improvement comprising a terminal at the other end of said resistor located adjacent the end of but seated entirely within the probe and having therein quick detachable connection means for connection with the apparatus, and an insulating compound potting said resistor within said probe without airgaps.
 10. Electrostatic spray apparatus comprising an electrically conductive normally grounded handle including a valve-operating trigger, an electrically insulating barrel and valve stem projecting forwardly from the upper end of the handle and the trigger, an electrically insulating nozzle assembly on the forward end of the barrel, a material inlet at the forward end of said barrel rearwardly of the nozzle assembly, an electrically insulating material supply tube inclined downwardly and rearwardly from the material inlet toward the lower end of the handle, conductive elements in the material-receiving portion of the barrel between said inlet and said nozzle assembly, means for carrying a high electrostatic charge to said conductive elements including an electrically insulating conductor-receiving tube generally paralleling said material supply tube, and a strap joining the lower ends of the handle and said tubes for physically supporting said tubes, said barrel, stem and material supply tube electrically isolating coating material from said grounded handle to accommodate spraying of both conductive and nonconductive coating materials.
 11. The apparatus of claim 10, including a ground fitting on the lower end of said conductor-receiving tube and a ground sheath of said tube connected to said fitting, said strap being electrically conductive and conductively secured to said fitting and handle. 